<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title></title>
    <style>
        body, ul, ol, li, img {
            margin: 0;
            padding: 0;
            list-style: none;
        }

        #box {
            width: 490px;
            height: 270px;
            padding: 5px;
            position: relative;
            border: 1px solid #ccc;
            margin: 100px auto 0;
        }

        .ad {
            width: 490px;
            height: 270px;
            overflow: hidden;
            position: relative;
        }

        #box img {
            width: 490px;
        }

        .ad ol {
            position: absolute;
            right: 10px;
            bottom: 10px;
        }

        .ad ol li {
            width: 20px;
            height: 20px;
            line-height: 20px;
            border: 1px solid #ccc;
            text-align: center;
            background: #fff;
            float: left;
            margin-right: 10px;
            cursor: pointer;
            _display: inline;
        }

        .ad ol li.current {
            background: yellow;
        }

        .ad ul li {
            float: left;
        }

        .ad ul {
            position: absolute;
            top: 0;
            width: 2940px;
        }

        .ad ul li.current {
            display: block;
        }

        #arr {
            display: none;
        }

        /* #box:hover #arr {
            display: block;
        } */

        #arr span {
            width: 40px;
            height: 40px;
            position: absolute;
            left: 5px;
            top: 50%;
            margin-top: -20px;
            background: #000;
            cursor: pointer;
            line-height: 40px;
            text-align: center;
            font-weight: bold;
            font-family: '黑体';
            font-size: 30px;
            color: #fff;
            opacity: 0.3;
            border: 1px solid #fff;
        }

        #arr #right {
            right: 5px;
            left: auto;
        }
    </style>

</head>
<body>
<div id="box" class="all">
    <div class="ad">
        <ul id="imgs">
            <li><img src="images/1.jpg"/></li>
            <li><img src="images/2.jpg"/></li>
            <li><img src="images/3.jpg"/></li>
            <li><img src="images/4.jpg"/></li>
            <li><img src="images/5.jpg"/></li>
        </ul>
    </div>

    <div id="arr"><span id="left">&lt;</span><span id="right">&gt;</span></div>
</div>


<script>
    const box=document.getElementById('box')
    const ulBox=document.querySelector('ul')
    const imgs=document.getElementById('imgs')

    //li的数量
    const liNumber=imgs.children.length
    //li的长度
    const liBoxLength=document.querySelector('li').offsetWidth
    const arr=document.getElementById('arr')
    const arrLeft=document.getElementById('left')
    const arrRight=document.getElementById('right')


    console.log(liNumber)
    // 左右轮播导航显示
    box.addEventListener('mouseover',()=>{
        arr.style.display='block'

    })

    box.addEventListener('mouseout',()=>{
        arr.style.display='none'
    })

    let currentIndex=0
    // 右导航
    arrRight.addEventListener('click',()=>{
        if(currentIndex<liNumber-1){
            currentIndex++
            console.log(currentIndex)
        }
        //位移长度
        const moveLength=currentIndex*liBoxLength
        moveAnimation(ulBox,-moveLength)


    })

    //左导航
    arrLeft.addEventListener('click',()=>{
        if(currentIndex>0){
            currentIndex--
            console.log(currentIndex)
        }
        //位移长度
        const moveLength=currentIndex*liBoxLength

        moveAnimation(ulBox,moveLength)

    })

    //下标



    //实现移动动画
    function moveAnimation(el,target){
        clearInterval(el.timer)
        let currentPosition=el.offsetLeft;
        const step=currentPosition<target?3:-3
        console.log(currentPosition)
        console.log(step)
        el.timer=setInterval(()=>{
            if(Math.abs(target-currentPosition)>Math.abs(step)){
                currentPosition+=step
                el.style.left=`${currentPosition}px`
                console.log(currentPosition)
            }else{
                el.style.left=`${target}px`
                clearInterval(el.timer)
            }

        },10)
    }

</script>
</body>
</html>
